Soil Erodibility of Hill and Rugged Terrain Landform in Rain Shadow Phusawan Watershed, Keang Krachan District, Petchauburi Province

Abstract

Pusawan wateshed area is 7 sq km where is rain shadow area and located in Keang Krachan
district, Petchauburi province. Rainfall intensity is not exceed 700 mm./year, elevation 90-400 m. MSL which
is consisted of 2 landforms, hill and rugged terrain. Hills is located in Southwest and Northeast which is
covered by mixed forest and bamboo forest. Rugged terrain is located in the middle of watershed area
which is agricultural area, deciduous especially, pineapple and fruit trees. The study aimed to investigate
soil erodibility for land suitability in watershed by dispersion ratio method. Soil samples were collected from
hill and rugged terrain area in 3 lines each. The total soil samples were 18 samples which were collected
3 samples in each line and elevation. The results found high erodibility due to dispersion ratio value was
ranged 12.1-58.7 which exceed than 10. Even though analysis of variance statistic was not different, but
dispersion ratio value in higher elevation was high. It might be concluded that soil erosion in watershed
was decreased by forest conservation in upstream and intensive soil conservation in agricultural area.